This is an Exposure Assessment Core Facility proposal to support a grant submitted in response to the RFA entitled Disease Investigation through Specialized Clinically-Oriented Ventures in Environmental Research (RFA ES-06-001). The purpose of the Exposure Assessment Core is to provide a centralized resource for the conduction of exposure assessment activities related to children's asthma research. The objectives are to provide, input into research design, field sampling equipment and support, and analytical services. Support of an Exposure Assessment Core Facility is justified based on the importance of exposure related activities associated with all research projects. As a result the EACwill serve an important research integration role. In addition, the Core will interact with the Data Management Core to provide exposure assessment data for integration into analyses.